1. Field of the Invention
This invention relates to a solar-cell-installed structure at least part of active electric portions of which stands exposed to surroundings, and a photovoltaic power generation system making use of the solar-cell-installed structure. More particularly, it relates to those which are characterized by having achieved more reduction of power loss by controlling leakage current.
2. Related Background Art
A rise in consciousness of environmental problems is more worldwide spreading than ever. In particular, apprehensions for the phenomenon of earth warming which is accompanied by emission of CO2 are serious, and there is an increasing eagerness for clean energy. At present, solar batteries can be said to be expectable as clean energy sources because of their safety and readiness to handle.
In recent years, various types have been proposed as forms of solar-battery assemblies. Besides the technical development on construction material integral-type solar battery in which a solar battery is incorporated in construction materials themselves, development is also made on conventional various stand installation systems.
Japanese Patent Application Laid-Open No. 11-270023 discloses a wall solar cell module the panel main body of which is formed of a concrete material. According to this publication, a solar cell module is integrally formed in a depression of a concrete panel and hence can be improved in building performance and maintenance performance.
Japanese Patent Application Laid-Open No. 2001-60704 discloses that a member on which a photoelectric transducer having a temporarily peelable film is to be attached may include concrete plates, slates, tiles and metal sheets. According to this publication, the temporarily peelable film constituting the photoelectric transducer brings about an improvement in construction (building or laying) performance and maintenance performance.
Japanese Utility Model Application Laid-Open No. 5-3430 discloses a power generation tile in which an opaque sheet is peelably fastened to the surface of a solar battery. According to this publication, in virtue of the sheet formed on the surface of a solar battery, the solar battery does not generate electric power during construction because it is covered with the sheet, promising safety during the construction, and also, in virtue of this sheet, the solar battery surface can be prevented from being scratched or contaminated during the construction.
Meanwhile, equipment of power plants or the like is all placed within controlled surroundings, and is placed in surroundings those who are not concerned, having no electrical knowledge, can not enter. Supposing such installation surroundings, development has been made on a solar battery some part of active electric portions of which stand exposed to surroundings.
FIGS. 11A and 11B are schematic views for illustrating a solar cell some part of electrodes of which stand exposed to surroundings. FIG. 11A illustrates a solar cell before formation of a weatherable coating film; and FIG. 11B, a solar cell after formation of the weatherable coating film. In the drawings, reference numeral 1101 denotes a photovoltaic device; 1102, a positive-pole electrode; 1103, a negative-pole electrode; and 1104, the weatherable coating film. Forming the weatherable coating film 1104 on the light-receiving side of the solar cell as shown in the drawings can make the solar cell have an outdoor weatherability. The part of the photovoltaic device 1101 is covered with the coating film to make the device have weatherability. However, the positive-pole electrode 1102 and the negative-pole electrode 1103 are not covered at least at the part electrically connected with an adjoining solar cell, and your hand can readily touch that part even after electrical interconnection has been made. Namely, the active electric portions partly stand exposed to surroundings.
However, in the case of solar-cell-installed structures in which supports are formed using, e.g., concrete materials, there has been a problem that the concrete materials may come to have a greatly low resistivity upon wetting, and hence electric current may greatly leak from the active electric portions standing exposed, resulting in a great power loss.
Moreover, such a great leakage current may unintentionally actuate a ground fault sensor of an inverter incorporated in the photovoltaic power generation system. As the result, the inverter may come inoperable.
An object of the present invention is to provide a solar-cell-installed structure which can lessen any leakage current flowing from solar cells, to reduce power loss.
Another object of the present invention is to provide a photovoltaic power generation system which can lessen any leakage current to prevent the inverter from stopping.
To achieve the above objects, the solar-cell-installed structure of the present invention comprises a solar cell at least part of active electric portions of which stands exposed to surroundings, and a support placed on the ground and on which support the solar cell is fixed,
wherein the support is in only spot or line contact with the ground.
In the solar-cell-installed structure of the present invention, the support may preferably be formed of a concrete material.
A back support which supports the support may also preferably be provided on the non-light-receiving side of the support, where the support may preferably be in only spot or line contact with the back support. The support may be platelike, and may more preferably satisfy the relation of:
t greater than 1,307.9(0.71+0.016xc2x7xcex8)/(dxc2x7gxc2x7cos xcex8),
where d is the density (kg/m3) of the support, g is the acceleration of gravity (m/s2) of the support, xcex8 is the angle of inclination of the support from the ground, and t is the thickness (m) of the support.
In another embodiment of the present invention, the solar-cell-installed structure may also comprise a solar cell at least part of active electric portions of which stands exposed to surroundings, and a support placed on the ground and on which support the solar cell is fixed,
wherein the support is in contact with the ground at least via an insulating member.
In this solar-cell-installed structure according to another embodiment of the present invention, the support may preferably be formed of a concrete material.
A back support which supports the support may also preferably be provided on the non-light-receiving side of the support, where the insulating member may more preferably be provided between the support and the back support. The support may be platelike, and may more preferably satisfy the relation of:
t greater than 1,307.9(0.71+0.016xc2x7xcex8)/(dxc2x7gxc2x7cos xcex8),
where d is the density (kg/m3) of the support, g is the acceleration of gravity (m/s2) of the support, xcex8 is the angle of inclination of the support from the ground, and t is the thickness (m) of the support.
The insulating member may also preferably have a surface tension of 28 mN/m or less.
The photovoltaic power generation system of the present invention comprises at least two solar-cell-installed structures (comprising the above solar-cell-installed structure) which are electrically interconnected, and an inverter provided internally with a ground fault sensor; the former interconnected structures being connected to the latter at the former""s positive and negative terminals.
In the photovoltaic power generation system of the present invention, the solar-cell-installed structures may be connected in series, and may preferably satisfy the relation of R greater than 5xc3x97Vxc3x97N, where N is the number of the solar-cell-installed structures connected in series, V is the voltage (V) of the photovoltaic power generation system, and R is the electrical resistance (xcexa9) between solar cells and the ground.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.